The second Jim Nelson guide to the Cascades has a bunch of routes in it of varying degrees of of difficulty:
Selected Climbs in the Cascades, Peter Potterfield & Jim Nelson, The Mountaineers, 1993, ISBN 0-89886-386-6.
Selected Climbs in the Cascades, Volume 2, Peter Potterfield & Jim Nelson, The Mountaineers, 2000, ISBN 0-89886-561-1.
Quite a lot of the routes in Beckey have also had winter ascents but I'm not sure any of them are done frequently due to the snow conditions in the Cascades. Access seems to be the biggest problem, Cuttthroat is only accessible when they open the pass for example.
Mt Index, , B1 p202
Dragontail Pk, Triple Couloirs (II/III, 5.8?), B1 p261
Colonial, Watusi Rodeo (IV), SC2 p164
Chair Peak, NE slab (WI3), SC1 p51
Cutthroat Peak, E face (III, WI4-5), SC2 p 182, April/May
There's some stuff on the Tooth too.
Ade